From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759691Ab2COIHU (ORCPT ); Thu, 15 Mar 2012 04:07:20 -0400 Received: from mx01.sz.bfs.de ([194.94.69.103]:39513 "EHLO mx01.sz.bfs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756307Ab2COIHH (ORCPT ); Thu, 15 Mar 2012 04:07:07 -0400 Message-ID: <4F61A328.8050302@bfs.de> Date: Thu, 15 Mar 2012 09:07:04 +0100 From: walter harms Reply-To: wharms@bfs.de User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; de; rv:1.9.1.16) Gecko/20101125 SUSE/3.0.11 Thunderbird/3.0.11 MIME-Version: 1.0 To: Julia Lawall CC: Guan Xuetao , Dan Carpenter , kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 7/7] arch/unicore32/kernel/dma.c: ensure arguments to request_irq and free_irq are compatible References: <1331494587-12196-1-git-send-email-Julia.Lawall@lip6.fr> <1331494587-12196-8-git-send-email-Julia.Lawall@lip6.fr> <1331513926.2048.58.camel@epip-laptop> <1331622633.2048.87.camel@epip-laptop> <1331712444.2389.36.camel@epip-laptop> <20120314081910.GC3163@mwanda> <1331714575.2389.47.camel@epip-laptop> <1331773284.2389.61.camel@epip-laptop> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 15.03.2012 07:10, schrieb Julia Lawall: > > > On Thu, 15 Mar 2012, Guan Xuetao wrote: > >> On Wed, 2012-03-14 at 10:23 +0100, Julia Lawall wrote: >>> >>> On Wed, 14 Mar 2012, Guan Xuetao wrote: >>> >>>> On Wed, 2012-03-14 at 11:19 +0300, Dan Carpenter wrote: >>>>> On Wed, Mar 14, 2012 at 04:07:24PM +0800, Guan Xuetao wrote: >>>>>> puv3_init_dma() is called ONCE when initializing. >>>>>> In logical, if request_irq(IRQ_DMAERR, *) failed, >>>>>> free_irq(IRQ_DMA, *) >>>>>> is unnecessary, and dma device/driver can keep on working. >>>>>> The patch could be: >>>>>> ret = request_irq(IRQ_DMAERR, dma_err_handler, 0, "DMAERR", >>>>>> NULL); >>>>>> if (ret) { >>>>>> printk(KERN_CRIT "Can't register IRQ for DMAERR\n"); >>>>>> - free_irq(IRQ_DMA, "DMA"); >>>>>> return ret; >>>>>> } >>>>> >>>>> It seems like you should remove the error return as well? >>>>> >>>>> regards, >>>>> dan carpenter >>>>> >>>> The error return value will only generate an extra warning message, and >>>> have no side-effect. >>> >>> The whole thing seems a little strange. I guess your point is that the >>> call site never looks at the return value? Wouldn't it be better to >>> make >>> there be no return value in that case? If there is a return value, some >>> calling context in the future might take that into account and then the >>> lack of a free_irq would be a memory leak. Also if the first >>> request_irq >>> can never fail, perhaps that should be made explicit by not testing the >>> return value? >>> >>> julia >> This function is an init_call, not a probe function, and it is only >> called ONCE. >> The dma device here has two interrupts, one IRQ_DMA, another IRQ_DMAERR. >> And the device could work without IRQ_DMAERR. >> The return value should indicate whether there is something wrong during >> initialization, so the function needs return errno when any request_irq >> is failed. >> For the first request_irq, some code has prepared its resources before >> this call, so I suppose it successful. However, the return value must be >> tested. > > OK, thank you for the explanation. I will change the patch. > hi Julia, would you mind to add the explaination to the code ? there is a good chance that someone will find the same problem again. re, wh